<!DOCTYPE html>
<html lang="en">
    <head>
        <title>css阻塞</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <style>
            h1 {
                color: red !important
            }
         </style>
        <script>
            function h () {
                console.log(document.querySelectorAll('h1'))
            }
            setTimeout(h, 0)
        </script>
        <link
            href="https://cdn.bootcss.com/bootstrap/4.0.0-alpha.6/css/bootstrap.css"
            rel="stylesheet">
    </head>
    <body>
        <h1>这是红色的</h1>
    </body>
</html>